Trigonal bipyramidal platinum complexes as models for ziegler-nasa catalytic sites

Five-coordinated η²-adducts of (+)-(S)-3-methyl-1-pentene (SMP) and (R,S)-3-methyl-1-pentene (RSMP) of the type [PtCl₂(η²-olefin)(α-di-hydrazone)] were prepared. In solution the more stable adducts are those which have the olefin presenting to Pt the face of opposite configuration to that of the chiral substituent. In the solid state the same situation is found by X-ray analysis for the adduct of SMP, while ¹H NMR studies point to the conclusion that the same configuration as the chiral substituent is preferred in the solid adduct of RSMP. These observations are compared with those in previous reports on coordination of SMP on square planar Pt and stereoselective polymerization.